Background: The 6-min walk distance (6MWD) predicts survival in pulmonary hypertension (PH). The peak oxygen consumption (V˙O2peak) measured during a cardiopulmonary exercise test (CPET) also relates to survival in PH, and it is unknown how the prognostic information from measurements of ventilatory responses and gas exchange during CPET compares to the prognostic information obtained by the 6MWD alone. The aims of our study were to compare prognostic values of different exercise parameters in PH and to assess whether CPET adds prognostic value to the information from the 6MWD.
Methods: After baseline right-heart catheterization and exercise testing, survival was assessed in a cohort of 115 PH patients.
Results: During the 4 yr of follow-up, 18 patients died. At baseline, pulmonary arterial pressure was 49 ± 17 mm Hg, the slope relating minute ventilation to carbon dioxide output (V˙E/V˙CO2slope) = 45 ± 11, V˙O2peak = 15 ± 6 mL·kg−1·min−1, increase in O2 pulse from rest to peak exercise (ΔO2 pulse) = 5 ± 2 mL·beat−1, and 6MWD = 445 ± 128 m. For the prediction of mortality, the areas under the receiver operating curves were very similar for the different parameters and ranged from 0.69 to 0.74. Patients with a V˙E/V˙CO2slope < 48, V˙O2peak > 13.2 mL·kg−1·min−1, ΔO2 pulse > 3.3 mL·beat−1, or a 6MWD > 399 m had a higher cumulative survival (P < 0.05). Multivariable Cox regression with a forward selection procedure showed that only ΔO2 pulse improved the univariate 6MWD prediction model significantly (P < 0.05).
Conclusion: CPET parameters predict survival in PH patients and add marginally to the prognostic value of the 6MWD.
1Institute for Cardiovascular Research and Department of Pulmonology, and 2Clinical Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, THE NETHERLANDS
Address for correspondence: Herman Groepenhoff, M.Sc., Department of Pulmonology, VU University Medical Center, De Boelelaan 1117, PO Box 7057, 1007 MB Amsterdam, The Netherlands; E-mail: firstname.lastname@example.org.
Submitted for publication March 2008.
Accepted for publication April 2008.